1. Technical Field
The present disclosure relates to active detecting techniques, and, more particularly, to a detecting system, a detecting device and a detecting method that can be easily operated to actively detect the presence of a target gas in a particular space.
2. Description of Related Art
Current gas detecting techniques based on metal oxide semiconductor technology offer the advantages of low cost, rapid measurement and long service life, and have been widely applied in the fields of home and industrial security. More specifically, the techniques generally use a sensor equipped with a metal oxide film and a heater to detect gas molecules, wherein the heater increases the temperature of the metal oxide film, such that the metal oxide film in the heating process reacts with the gas molecules in the environment, thereby changing the resistance of the metal oxide film to output a corresponding sensing signal. The sensing signal is then compared and analyzed to determine the various characteristics of the gas.
However, in actual use, the reaction between the metal oxide film and the gas molecules is limited by numerous environmental factors, such as temperature, humidity and the like, such that the output sensing signal is accompanied by a phenomenon called signal drift. As a result, accurate results in subsequent comparison and analysis may not be obtained. In addition, when the gas molecules are combined of gases in the same group, for example, methanol and ethanol, are mixed together, the reaction temperature and other characteristics of the gas molecules in the same group are very similar, so the current detection methods, upon completing comparison and analysis on the sensing signal, may have difficulties in obtaining accurate concentrations or mixing ratio of the gas molecules.
Existing detection methods can be found in prior-art publications, such as U.S. Pat. Nos. 6,739,180, 7,350,396, 7,460,958 and 7,680,607. U.S. Pat. Nos. 6,739,180 and 7,350,396 simply achieve detection through signal comparison, but they did not offer a solution to the problem of signal drift, and they lack sufficient accuracy in terms of concentration determination. In addition, they did not disclose any method for identifying the mixtures containing the gases in the same group, such as a mixture containing both methanol and ethanol. U.S. Pat. No. 7,460,958 determines concentrations according to a prediction module, but in its actual implementation, the method requires each sensor in a sensor array to perform self-diagnosis and compensation, and thus increasing the cost and time for detection. The chemical analyte technique proposed by U.S. Pat. No. 7,680,607 also requires a plurality of metal oxide sensors for signal comparison, thus resulting in waste of detection time and cost. In addition, it also fails to address the signal drift caused by the ambient temperature and humidity.
In another aspect, the implementations of the existing gas detecting technology usually require bulky and costly testing equipment. As such, it fails to analyze the gases in real time, and also hardly to be applied in our daily life. For example, the market is flooded with many poor-quality alcoholic beverages that contain harmful methanol, if one wishes to determine whether a beverage contains harmful substances, the only way is to retrieve samples of the alcoholic beverage and send them to specific authorities for time-consuming detection.
Therefore, there is a need for a solution that addresses the abovementioned and other shortcoming in the conventional gas detecting technique.